WASHINGTON — A renewed bipartisan push to rewrite U.S. immigration laws presents Republicans with their clearest opportunity to make up lost ground with one of the fastest growing forces in American politics.

Sen. John McCain, R-Ariz., said Monday after a group of eight senators unveiled an immigration overhaul plan that includes a pathway to citizenship for the estimated 11 million illegal residents "We cannot continue as a nation with 11 million people hiding in the shadows," McCain said.

For the GOP, their viability in national elections may also depend on it.

"You cannot win a national election and lose Hispanics at a rate Mitt Romney did," said Amy Walter, an election analyst for the non-partisan Cook Political Report.

Hispanics voted overwhelmingly for President Obama over Republican nominee Mitt Romney in the 2012, and the Democratic margin of victory has increased in each of the past two presidential elections. Hispanics accounted for 10% of the national electorate in 2012 — an amount that will grow in future elections as the nation's Hispanic population rises. The Pew Hispanic Center estimates the Hispanic share of the electorate will double by 2030.

"I do believe that (Republicans) have a compelling message for Hispanics, so if we can get this issue behind us, then we are on much more fertile ground to try and take more of their vote share," said Rob Jesmer, a former Senate GOP campaign strategist who oversaw the 2010 and 2012 election cycles. "But as long as this issue is out there it's going to be very problematic for us to make gains."

Republicans also face a "compassion gap" with Hispanics. A September 2012 Pew survey showed 10% said the Republican Party cares more about Hispanics compared to 61% for the Democratic Party.

"The trend line is against us," said Republican strategist Kevin Madden, a former Romney campaign aide. "The challenge becomes more and more daunting if we don't do it now."

The long-term incentive for Republicans to reshape their party's reputation among Hispanics is likely to meet resistance in the short-term by lawmakers wary of tackling an issue that has historically divided the GOP and raises the threat of intraparty challenges. Republican incumbents supporting the plan may find they have conservatives lining up to challenge them in primaries.

In Iowa, for instance, where the retirement of Democratic Sen. Tom Harkin has created an open seat race in 2014, potential GOP candidates include Rep. Steve King, a conservative voice on immigration who opposes a pathway to citizenship for illegal immigrants.

"A candidate who supports citizenship for people who broke the law to enter the country will have to carefully explain that to primary voters," said former Iowa GOP chairman Steve Grubbs, although he noted that economic issues "consistently trump immigration as a voting issue."

Outside forces are already mobilizing. NumbersUSA, an advocacy group that opposes a pathway to citizenship and played a role in defeating a similar 2007 immigration bill, announced Monday they were calling on 1.3 million members to oppose the Senate compromise which they called an effort to "out-amnesty Obama."

"It'll be bumpy," Jesmer said.

Lynn Tramonte, deputy director of America's Voice Education Fund, an advocacy group that supports the Senate compromise, said conservatives' fear of a reprisal from voters is overestimated based on recent election results. "It's a myth that it's this huge motivating issue for this huge segment of Republican base voters,'' she says, pointing to early 2012 Republican presidential primaries in Iowa, South Carolina and Florida, where immigration was not a decisive issue. South Carolina will also have two Senate races in 2014 due to the retirement of former senator Jim DeMint last month.

House Republican leaders were notably silent Monday in the wake of the bipartisan Senate compromise announcement. A spokesman for House Speaker John Boehner, R-Ohio, said only that the speaker was eager to hear more from Sen. Marco Rubio, R-Fla., a prospective 2016 presidential candidate who supports the Senate deal. Rubio's involvement underscores the political importance of an issue that could propel the junior senator on the national stage.

"I think he is in many ways something of a pied piper for Republican conservatives, and they will follow him wherever he goes," Walter said.

To reap the potential political benefits, Republicans will have to get it through the House, where Rep. Paul Ryan, R-Wis., another 2016 prospective candidate, has aligned himself with Rubio. "It's kind of a new day," Tramonte said. "For (Republicans) to really benefit politically, this reform has to become law. If it doesn't, they're going to give Democrats a talking point to use against them in future elections."